The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed.
For example, light diffraction in an optical lithography system becomes an obstacle for further scaling down the feature size. Common techniques used to decrease the light diffraction impact includes an optical proximity correction (OPC), a phase shift mask (PSM), and an immersion optical lithography system. A charged particle lithography system is another alternative to scale down the feature size. One of the challenges in the charged particle lithography system is to level a resist film deposited on a substrate for exposing the resist film by an optical sensor. Another challenge is electric static charges on the resist film in the charged particle lithography system
Accordingly, what is needed is a method or an apparatus to address the issues in the charged particle lithography process.